This article details philosophical responses to the problem posed by the existence, whether real or perceived, of priestcraft, a problem that boiled down to a fear that if the custodians of God’s tabernacle were corrupt, so too were the contents of the tabernacle. It first explores the attempts of Edward Herbert and Thomas Hobbes to guarantee the truth of revealed matters of faith in response to their perception of widespread priestcraft, arguing that, while each sought to undermine sacerdotal authority, they (...) ultimately exempted matters of faith from the litmus test of reason. This resulted in a less-than-satisfactory solution to the problem. It turns next to Locke’s Essay (1690) and The Reasonableness of Christianity (1695), exploring how empirical notions of evidence, fact, and probability, as framed in these works, enabled a radical re-evaluation of the grounds of Christian faith, which subsequently influenced the writings of John Toland, Anthony Collins, and Peter Annet between the 1690s and 1740s. These “Lockean free-thinkers,” it argues, were in fact closer to the position of the Essay and Reasonableness than to the deism of Edward Herbert in their efforts to tackle priestcraft. Concluding, this article proposes that the problem of priestcraft served as a catalyst for early modern British philosophers to increasingly narrow the grounds of faith, until faith was deemed legitimate only when grounded upon fact. (shrink)